Concentration ratio measuring method and concentration ratio measuring device

Abstract

To provide a concentration ratio measuring method that can execute measurement of the concentration ratio of a toluene- or methylcyclohexane-containing solution, for a long period of time, within a wide concentration range, in real time, and with high reliability.SOLUTION: A concentration ratio measuring method includes the steps of: measuring the absorbance A(λC)T0 of a solution at a correction wavelength λC at the start of measurement T0, the absorbance A(λC)T1 of the solution at the correction wavelength λC after the lapse of predetermined time T1, and the absorbance A(λS)T1 of the solution at a specific wavelength λS after the lapse of predetermined time T1; and correcting the absorbance A(λS)T1 on the basis of the following formula (I) to calculate a correction value A'(λS)T1, and on the basis of the correction value A'(λS)T1, calculating the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane on the basis of a calibration curve recorded in advance.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a concentration ratio measuring method and a concentration ratio measuring device. [Background technology]

[0002] The use of hydrogen energy is being promoted as a decarbonized energy source. Hydrogen has a low energy density in gaseous form and is difficult to transport, so a technology known as the organic hydride system has been reported as a hydrogen storage and transportation technology, in which hydrogen is reacted with toluene to synthesize methylcyclohexane as a hydrogen storage medium, the methylcyclohexane is transported, and hydrogen is extracted from the methylcyclohexane by dehydrogenation (see, for example, Patent Document 1, etc.).

[0003] As a method for determining the concentration ratio of toluene and methylcyclohexane in a synthesis reaction or a dehydrogenation reaction of methylcyclohexane, a method is known in which the reaction solution after synthesis is measured by a mass spectrometer such as gas chromatography to determine the concentrations of toluene and methylcyclohexane in the reaction solution, and the conversion rate is calculated from the concentrations of both (see, for example, Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-095329 [Patent Document 2] JP 2020-159743 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional gas chromatography measurement method, the concentration of the component to be measured in the measurement sample must be sufficiently low, so the measurement sample must be sampled, sufficiently diluted with a solvent, and then presented to a gas chromatography device. Therefore, although the conventional measurement method has high measurement accuracy, it is difficult to measure the concentration in a wide concentration range in real time, and automation is difficult.

[0006] The present disclosure aims to provide a concentration ratio measurement method and a concentration ratio measurement device that can perform reliable measurement of the concentration ratio of a solution containing toluene or methylcyclohexane in real time over a wide concentration range over a long period of time. [Means for solving the problem]

[0007] As a means for solving the above problems, a concentration ratio measurement method according to one embodiment of the present disclosure is a concentration ratio measurement method for measuring a concentration ratio of a solution containing toluene to methylcyclohexane, comprising the steps of: Correction wavelength λ at the start of measurement T0 C The absorbance A (λ C ) T0 and measuring After a predetermined time has elapsed, the correction wavelength λ of T1 C The absorbance A (λ C ) T1 and measuring After a certain time has elapsed, the specific wavelength λ of T1 S The absorbance A (λ S ) T1 and measuring The absorbance A (λ S ) T1 Correct the correction value A'(λ S ) T1 Calculate

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[0008] According to the present disclosure, it is possible to provide a concentration ratio measurement method and a concentration ratio measurement device that can perform reliable measurement of the concentration ratio of a solution containing toluene or methylcyclohexane in real time over a wide concentration range over a long period of time. [Brief description of the drawings]

[0009] [Figure 1] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1000 nm to 2500 nm. [Diagram 2] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination. [Diagram 3] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1100 nm to 1300 nm. [Figure 4] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1600 nm to 1800 nm. [Diagram 5] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 2000 nm to 2200 nm. [Figure 6]1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 2200 nm to 2500 nm. [Figure 7] 4 is a flowchart showing an example of a concentration ratio measuring method in the first embodiment. [Figure 8] 10 is a flowchart showing an example of a concentration ratio measuring method in the second embodiment. [Figure 9] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1000 nm to 1100 nm. [Figure 10] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1280 nm to 1380 nm. [Figure 11] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1520 nm to 1620 nm. [Figure 12] 13 is a flowchart showing an example of a concentration ratio measuring method according to the third embodiment. [Figure 13] FIG. 13 is a schematic diagram showing an example of a concentration ratio measuring device according to a fourth embodiment. [Figure 14] FIG. 13 is a schematic diagram showing an example of a concentration ratio measuring device according to a fifth embodiment. [Figure 15] FIG. 13 is a schematic diagram showing another example of the concentration ratio measuring device in the fourth embodiment. [Figure 16] FIG. 13 is a schematic diagram showing another example of the concentration ratio measuring device in the fourth embodiment. [Figure 17] FIG. 13 is a schematic diagram showing another example of the concentration ratio measuring device in the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, each embodiment will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and redundant description will be omitted.

[0011] (Concentration ratio measuring method and concentration ratio measuring device) The concentration ratio measurement method of the present disclosure includes an absorbance measurement step and a concentration ratio calculation step, and preferably has a first discrimination step and a second discrimination step, and may further have other steps such as a wavelength setting step and a calibration curve creation step as necessary. The concentration ratio measurement device of the present disclosure includes an absorbance measurement section and a concentration ratio calculation section, and preferably includes a first discrimination section and a second discrimination section, and further includes other members as necessary. Below, matters common to the concentration ratio measuring method and the concentration ratio measuring device will be described together.

[0012] -Methylcyclohexane synthesis and dehydrogenation reaction- First, the synthesis reaction of methylcyclohexane as a hydrogen storage medium and the dehydrogenation reaction for extracting hydrogen will be described. Toluene (C6H5CH3) and hydrogen (H2) are reacted to produce methylcyclohexane (C6H 11 The reaction to synthesize CH3) (also called hydrogen addition reaction) is represented by the following reaction formula (1).

[0013] <Reaction formula (1)> C6H5CH3+ 3H2→ C6H 11 CH3

[0014] The synthesis reaction of methylcyclohexane can be carried out by a known method, and examples of such methods include a method of reacting toluene with hydrogen; and a method of synthesizing methylcyclohexane from water and toluene without passing through hydrogen gas by directly subjecting toluene to an electrochemical reaction. Once the hydrogenation reaction is started, the reaction system usually needs to be cooled since the hydrogenation reaction itself is an exothermic reaction. If the reaction temperature significantly exceeds 100.9°C, the boiling point of methylcyclohexane under atmospheric pressure, the synthesis efficiency of methylcyclohexane (hereinafter sometimes referred to as "conversion rate") decreases. Therefore, it is preferable to maintain the reaction temperature so that it does not rise too much, for example, by using a cooling device or a cooling water line. The reaction temperature is usually 80°C to 100°C, preferably 85°C to 98°C, and more preferably 85°C to 96°C.

[0015] The dehydrogenation reaction for extracting hydrogen from methylcyclohexane is represented by the following reaction formula (2), which is the reverse reaction of the above reaction formula (1). The dehydrogenation reaction can be carried out by a known method.

[0016] <Reaction formula (2)> C6H 11 CH3 → C6H5CH3+ 3H2

[0017] The concentration ratio measuring method and the concentration ratio measuring device can be suitably applied to the measurement of the concentration ratio of toluene to methylcyclohexane in a solution resulting from such a synthesis reaction or dehydrogenation reaction of methylcyclohexane. According to the concentration ratio measurement method and concentration ratio measurement device, the concentration ratio can be measured over a wide concentration range from 0 volume % to 100 volume % methylcyclohexane without the need for a dilution process that is required in the conventional measurement method using gas chromatography. This makes it possible to perform real-time measurement and to automate the measurement. By measuring the concentration ratio in the solution after the reaction, the conversion rate and dehydrogenation efficiency of methylcyclohexane in the resulting reaction solution can be easily evaluated over a wide concentration range. The concentration ratio can be measured in real time in the solution during the reaction process, which allows the optimization of the reaction apparatus and reaction conditions. In addition, by correcting the absorbance at a specific wavelength using a correction wavelength, reliable measurements can be performed in real time over a wide concentration range over a long period of time.

[0018] <Solution> The solution containing toluene to methylcyclohexane that is the subject of measurement is a solution containing at least one of toluene and methylcyclohexane, and may be a solution containing either toluene or methylcyclohexane, or may contain both toluene and methylcyclohexane, and the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m may be any concentration ratio, and in either case, the measurement can be performed suitably.

[0019] The solution contains at least one of toluene and methylcyclohexane, and may further contain other components as necessary, but preferably consists essentially of at least one of toluene and methylcyclohexane. The content of at least one of toluene and methylcyclohexane in the solution is, in terms of volume ratio to the total amount of the solution, preferably 95% by volume or more, more preferably 98% by volume or more, and even more preferably 99% by volume or more.

[0020] The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other components include by-products such as benzene and methane; and components derived from catalysts and reaction equipment in the synthesis reaction and dehydrogenation reaction of methylcyclohexane.

[0021] [First embodiment] <Absorbance measurement step and absorbance measurement unit> The absorbance measurement step is performed at a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N This is a step of measuring the absorbance of the solution, and can be suitably performed by the absorbance measuring unit. The absorbance measurement unit detects a correction wavelength λ C , specific wavelength λS , and optionally a non-absorbing wavelength λ N Specifically, it is preferable that the measurement device has a measurement cell, a light source which irradiates the solution contained in the measurement cell with light of a specific wavelength, and an absorbance detector which measures the absorbance of the transmitted light which has passed through the solution, and further has a lens, a spectroscope, an optical fiber, etc., as necessary.

[0022] <Concentration ratio calculation step and concentration ratio calculation unit> The concentration ratio calculation step is carried out based on the following formula (I) to calculate a specific wavelength λ of T1 after a predetermined time has elapsed. S The absorbance A (λ S ) T1 Correct the correction value A'(λ S ) T1 Calculate the correction value A'(λ S ) T1 and calculating a concentration ratio t:m of the concentration t of the toluene and the concentration m of the methylcyclohexane based on a previously recorded calibration curve. This can be suitably performed by the concentration ratio calculation unit. The concentration ratio calculation unit calculates a specific wavelength λ of T1 after a predetermined time has elapsed based on the following formula (I): S The absorbance A (λ S ) T1 Correct the correction value A'(λ S ) T1 Calculate the correction value A'(λ S ) T1 and a unit for calculating a concentration ratio t:m of the concentration t of toluene and the concentration m of methylcyclohexane based on a previously recorded calibration curve based on the above formula (I) and formulas (1) and (2) described below.

[0023]

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[0024] Specifically, the absorbance measurement step and the absorbance measurement unit are C The absorbance A (λ C ) T0 and the correction wavelength λ of T1 after a predetermined time has elapsed. C The absorbance A (λ C ) T1 After a certain time has elapsed, the specific wavelength λ of T1 S The absorbance A (λ S ) T1 At least, measure:

[0025] The measurement start time T0 is not particularly limited and may be set at any time point depending on the purpose, but is preferably the time point when the absorbance measurement unit to be used is calibrated or any time point after a certain time has elapsed since the time point of calibration. Here, the certain period of time means a period of time after calibration during which it can be considered that no error occurs in the absorbance measurement unit. The time T1 at the time T1 after a predetermined time has elapsed from the measurement start time T0 or the predetermined time is not particularly limited and can be appropriately selected depending on the purpose.

[0026] -Specific wavelength λ S - The specific wavelength λ SThe wavelengths are one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

[0027] FIG. 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1000 nm to 2500 nm. FIG. 2 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination, and is a graph in which the relationship between the coefficient of determination is superimposed on the graph of FIG. In Figures 1 and 2, the vertical axis indicates absorbance, and the horizontal axis indicates wavelength. Solutions (represented as T00M100, T10M90, T30M70, T50M50, T70M30, and T100M00 in Figures 1 and 2) were prepared so that the concentration ratio t:m of the concentration t of toluene to the concentration m of methylcyclohexane was 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively, in terms of volume [L], and the absorbance of each solution was measured at wavelengths of 1000 [nm] to 2500 [nm]. In Figure 2, the bold line indicates the coefficient of determination R 2 (Correlation coefficient R squared: R 2 ) and the right vertical axis shows the coefficient of determination.

[0028] As is apparent from FIGS. 1 and 2 and the examples shown below, the specific wavelength λ S is a wavelength or wavelength range where a good correlation is obtained between the concentration ratio t:m of the concentration t of toluene to the concentration m of methylcyclohexane, and the absorbance, and where the coefficient of determination is close to 1. Therefore, at a specific wavelength λ S By measuring the absorbance of the solution at t:m and calculating the concentration ratio t:m based on the absorbance, it is possible to measure the concentration ratio over a wide concentration range from 0 volume % to 100 volume % methylcyclohexane, and also to measure the concentration ratio in real time without pretreatment of the solution.

[0029] In addition, when the solution contains other components that affect the absorbance of the solution at wavelengths specific to the other components, a concentration ratio measurement method with high measurement accuracy can be implemented by setting the specific wavelength so as not to include the wavelengths specific to the other components.

[0030] -Correction wavelength λ C - The correction wavelength λ C is the correction wavelength λ C the product of the molar absorption coefficient of toluene and the molar concentration of toluene at C is a wavelength at which the product of the molar absorption coefficient of methylcyclohexane and the molar concentration of methylcyclohexane is approximately equal. In other words, the correction wavelength λ C is a wavelength at which a constant absorbance is exhibited regardless of the concentration ratio of toluene and methylcyclohexane in the solution. The correction wavelength λ C is preferably one or more of the wavelengths of 1160 nm or more and 1166 nm or less, 1694 nm or more and 1707 nm or less, 2086 nm or more and 2090 nm or less, and 2274 nm or more and 2284 nm or less.

[0031] While the concentration ratio can be measured based on the absorbance at a specific wavelength, when the concentration ratio is measured over a long period of time, for example, one hour or more while the hydrogenation and dehydrogenation reactions of toluene and methylcyclohexane are progressing, measurement errors may occur over time even if the measurement device is calibrated. For example, the optical path length of the measurement cell may change. Since absorbance is proportional to the optical path length, for example, if the optical path length of the measurement cell is increased by 10%, the absorbance also increases by 10%, resulting in a measurement error.

[0032] FIG. 3 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the wavelength range of 1100 nm to 1300 nm, and is an enlarged graph of the graph of FIG. 1 with the wavelengths of 1100 nm to 1300 nm limited. In FIG. 3, it can be seen that the absorbance of the solution near a wavelength of 1163 nm is constant regardless of the concentration ratio of the solution. Here, the correction wavelength λ C Absorbance A (λ C ) can be represented by the following formula (II).

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[0033] A(λ C ): Correction wavelength λ C Absorbance at [AU] α T (λ C ): λ C Molar absorptivity of toluene in [L mol -1 ·cm -1 ] α M (λ C ): λ C Molar absorptivity of methylcyclohexane in [L mol -1 ·cm -1 ] D: Optical path length [cm] c T : Molar concentration of toluene [mol L -1 ] c M : Molar concentration of methylcyclohexane [mol L -1 ] t: Concentration ratio of toluene in the solution (volume ratio) m: Concentration ratio (volume ratio) of methylcyclohexane in the solution where t+m=1

[0034] Since the absorbance is constant regardless of the concentration ratio of the solution, the correction wavelength λ C the product of the molar absorption coefficient of toluene and the molar concentration of toluene at C The molar absorption coefficient of methylcyclohexane in is equal to the product of the molar concentration of methylcyclohexane. Therefore, the formula: α T (λ C )×c T = α M (λC )×c M By substituting the above, it can be expressed by the following formula (III).

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[0035] From the above formula (III), the correction wavelength λ C Absorbance A (λ C ) is proportional to the optical path length D, regardless of the concentration ratio of the solutions. Therefore, it can be expressed as the following formula (IV), and it can be seen that regardless of the concentration ratio of the solutions, the change in absorbance from the start of measurement T0 to a predetermined time T1 is equal to the change in optical path length from the start of measurement T0 to a predetermined time T1.

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[0036] Therefore, based on the following formula (I), by multiplying the coefficient of the above formula (IV) (sometimes referred to as a correction coefficient), the specific wavelength λ of T1 after a predetermined time has elapsed can be calculated. S The absorbance A (λ S ) T1 can be corrected. In other words, even when the hydrogenation and dehydrogenation reactions of toluene and methylcyclohexane progress and the concentration ratio changes from moment to moment, the correction wavelength λ C Absorbance A (λ C) the relationship of the above formula (IV) is established, and the specific wavelength λ of T1 after a predetermined time has elapsed is calculated based on the following formula (I) by using a correction coefficient. S The absorbance A (λ S ) T1 can be corrected. The calculated correction value A'(λ S ) T1 By calculating the concentration ratio based on this, highly reliable measurements can be performed in real time over a wide concentration range over a long period of time.

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[0037] The above correction wavelength λ C The explanation of the above can be applied to the vicinity of 1706 nm (see FIG. 4), 2090 nm (see FIG. 5), and 2284 nm (see FIG. 6) in addition to the vicinity of 1163 nm (see FIG. 3). C This allows correction of the optical path length. 4 to 6 are graphs showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance at 1600 nm to 1800 nm, 2000 nm to 2200 nm, and 2200 nm to 2500 nm, respectively. 4 to 6, it can be seen that the absorbance of the solutions at around 1706 nm (see FIG. 4), around 2090 nm (see FIG. 5), and around 2284 nm (see FIG. 6), respectively, shows a constant absorbance regardless of the concentration ratio of the solutions, similar to the absorbance at around 1163 nm (see FIG. 3).

[0038] FIG. 7 shows a flowchart illustrating an example of a concentration ratio measuring method in the first embodiment. First, the correction wavelength λ for the measurement start time T0 C The absorbance A (λ C ) T0 (Step S1-1), and then, after a predetermined time has elapsed, the correction wavelength λ of T1 is measured. C The absorbance A (λ C ) T1(Step S1-2), and at the same time, after a predetermined time has elapsed, a specific wavelength λ of T1 is measured. S The absorbance A (λ S ) T1 is measured (step S1-3). Based on the formula (I), the absorbance A (λ S ) T1 Correct the correction value A'(λ S ) T1 (Step S2-1), and the calculated correction value A'(λ S ) T1 The concentration ratio t:m of toluene to methylcyclohexane is calculated based on the formula (2) (step S2-2).

[0039] [Second embodiment] It is preferable that the concentration ratio measurement method further comprises, as a first discrimination step, a step of discriminating whether the measurement is abnormal or normal on the basis of a correction coefficient. That is, the concentration ratio measurement method is C ) T0 The absorbance A (λ C ) T1 The correction coefficient A (λ C ) T0 / A(λ C ) T1 It is preferable that the method further comprises a step of determining whether a predetermined band value is satisfied, continuing the measurement if the predetermined band value is satisfied, and terminating the measurement if the predetermined band value is not satisfied. The concentration ratio measuring device also detects the absorbance A(λ C ) T1 The absorbance A (λ C ) T0 The ratio A(λ C ) T0 / A(λ C ) T1 It is preferable that the measurement device further includes a first discrimination unit that discriminates whether a predetermined band value is satisfied, continues the measurement if the predetermined band value is satisfied, and terminates the measurement if the predetermined band value is not satisfied.

[0040] The predetermined band value is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.9 to 1.1, more preferably 0.95 to 1.05, and even more preferably 0.97 to 1.03. As a result, the ratio A(λ C ) T0 / A(λ C ) T1 However, if the measured value does not meet the predetermined band value, it can be determined that the optical path length has changed more than expected, causing an abnormality in the measurement system, and the measurement is terminated.If the measured value meets the predetermined band value, the measurement is being carried out within the expected range, and the measurement can be continued.

[0041] FIG. 8 shows a flowchart illustrating an example of a concentration ratio measuring method in the second embodiment. Following step S1-3, in step S3, A(λ C ) T0 / A(λ C ) T1 7 except that a step of determining whether a predetermined band value is satisfied is performed.

[0042] [Third embodiment] It is preferable that the concentration ratio measurement method further comprises, as a second discrimination step, a step of discriminating whether the measurement is abnormal or normal based on the absorbance at a non-absorption wavelength. That is, the concentration ratio measurement method is performed by detecting the non-absorption wavelength λ of T1 after a predetermined time has elapsed. N The absorbance A (λ N ) T1 and measuring the absorbance A(λ N ) T1 satisfies a predetermined band value, continuing the measurement if the predetermined band value is satisfied, and terminating the measurement if the predetermined band value is not satisfied. In addition, the concentration ratio measuring device is configured such that the absorbance measuring unit detects a non-absorption wavelength λ of T1 after a predetermined time has elapsed. N The absorbance A (λ N ) T1The concentration ratio measuring device further measures the non-absorption wavelength λ of T1 after a predetermined time has elapsed. N The absorbance A (λ N ) T1 It is preferable that the measurement device further comprises a second determination unit that determines whether or not a predetermined band value is satisfied, continues the measurement if the predetermined band value is satisfied, and ends the measurement if the predetermined band value is not satisfied.

[0043] - non-absorption wavelength λ N - The non-absorption wavelength λ N is the non-absorption wavelength λ N The molar absorption coefficient of toluene at the non-absorption wavelength λ N and the molar absorption coefficient of methylcyclohexane at 1000 nm are both approximately zero. In other words, the non-absorption wavelength λ N is a wavelength at which almost no absorbance is detected, regardless of the concentration ratio of toluene and methylcyclohexane in the solution, and is a wavelength that is almost not absorbed by either toluene or methylcyclohexane. The non-absorption wavelength λ N However, it is preferable that the wavelength is one or more of 1000 nm or more and 1100 nm or less, 1300 nm or more and 1340 nm or less, and 1540 nm or more and 1600 nm or less.

[0044] The predetermined band value is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0 or more and 0.1 or less, more preferably 0 or more and 0.05 or less, and even more preferably 0 or more and 0.03 or less. This allows the absorbance A (λ N ) T1 However, if the measured value does not meet the predetermined band value, it can be determined that the output of the light source has changed more than expected, causing an abnormality in the measurement system, and the measurement is terminated.If the measured value meets the predetermined band value, the measurement is performed within the expected range, and the measurement can be continued.

[0045] 9 to 11 are graphs showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance at 1000 nm to 1100 nm, 1280 nm to 1380 nm, and 1520 nm to 1620 nm, respectively. 9 to 11, it can be seen that the absorbance of the solutions at 1000 nm to 1100 nm (see FIG. 9), 1300 nm to 1340 nm (see FIG. 10), and 1540 nm to 1600 nm (see FIG. 11) is approximately zero regardless of the concentration ratio of the solutions. This means that wavelengths in this vicinity are not absorbed in either toluene or methylcyclohexane.

[0046] Taking the vicinity of 1560 nm (see Figure 11) as an example, if the absorbance around 1560 nm changes, it indicates a change in the light source. If the absorbance increases at wavelengths that are not absorbed, it is possible that the light source has deteriorated for some reason, causing a decrease in luminous flux. On the other hand, if the absorbance in the vicinity of 1560 nm is decreasing (specifically, becoming negative), then there is a possibility that the light source has become brighter due to some cause, such as an increase in the drive current of the light source. Thus, the non-absorption wavelength λ N If the absorbance of the sample changes significantly, the measurement is interrupted and calibration is performed again.

[0047] FIG. 12 shows a flowchart illustrating an example of a concentration ratio measuring method in the third embodiment. Following step S3, in step S4, the non-absorbed absorbance A (λ N ) T1 satisfies a predetermined band value. It is to be noted that only step S3 or step S4 may be performed. Furthermore, the order of performing steps S3 and S4 may be interchangeable, and steps S3 and S4 may be performed simultaneously.

[0048] [Fourth embodiment: Correction of fluctuations in light source] The concentration ratio measurement method is performed at a non-absorption wavelength λ N It is preferable that the method further comprises a step of correcting the fluctuation of the light source based on the absorbance (second correction step). That is, the concentration ratio measurement method is performed by measuring the non-absorption wavelength λ N The transmitted light intensity I(λ N ) T0 and the non-absorption wavelength λ after a predetermined time T1 N The transmitted light intensity I(λ N ) T1 and measuring Based on the following formula (V), after a certain time has elapsed, the specific wavelength λ of T1 S The absorbance A (λ S ) T1 Correction is made to the correction value A''(λ S ) T1 It is preferable that the method further comprises the step of calculating

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[0049] Here, when the correction for the variation of the light source based on the formula (I) and the correction based on the formula (V) are performed, the order of the corrections is not particularly limited and can be appropriately selected depending on the purpose. Either correction can be performed first, but it is preferable to perform the correction based on the formula (V) first and then use the calculated correction value A″(λ S ) T1 is expressed as the absorbance A (λ S ) T1 It is preferable to substitute That is, the specific wavelength λ in formula (I) Sand correction wavelength λ C The absorbance of is affected by variations in the light source, while the non-absorbing wavelength λ in formula (V) N Since the absorbance of is almost 0, it is considered that the formula (V) is almost unaffected by the optical path length. Therefore, after first correcting the effect of the fluctuation of the light source by the formula (V), the correction value A''(λ S ) T1 It is preferable to correct the optical path length according to formula (I) using:

[0050] In addition, the concentration ratio measuring device is configured such that the absorbance measuring unit detects a non-absorption wavelength λ N The transmitted light intensity I(λ N ) T0 and the non-absorption wavelength λ after a predetermined time T1 N The transmitted light intensity I(λ N ) T1 is further measured, and the concentration ratio calculation unit calculates the specific wavelength λ of T1 after a predetermined time has elapsed based on the formula (V). S The absorbance A (λ S ) T1 Correction is made to the correction value A''(λ S ) T1 Calculate.

[0051] Formulae (VI) to (XIII) for deriving formula (V) will be explained in order below. Specific wavelength λ at the start of measurement T0 S Absorbance A (λ S ) T0 can be expressed as the following (VI) based on the relation between absorbance and transmittance.

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[0052] Similarly, after a predetermined time has elapsed, the specific wavelength λ of T1 S Absorbance A (λ S ) T1 can be calculated from the following (VII).

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[0053] Here, the denominator on the right side is the specific wavelength λ at the start of measurement T0. S The incident light intensity I0(λ S ) T0 The reason for using the above is that the incident light intensity I0(λ S ) T0 This is because the incident light intensity is not measured after the predetermined time T1 has elapsed, but only the incident light intensity is measured. However, in reality, the light source and the incident light intensity gradually change. Therefore, if we assume that only the light source changes b in an environment where factors other than the light source do not change at a certain time T1 after the measurement start time T0, the incident light intensity at the certain time T1 can be expressed by the following formula (VIII).

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[0054] Moreover, the transmitted light intensity T1 after a predetermined time has elapsed can be expressed by the following formula (IX).

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[0055] By substituting the above formula (VIII) into the above formula (VII), it can be converted into the following formula (X).

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[0056] Here, the correction value A'(λ S ) T1 is represented by the following formula (XI) by replacing the above formula (X).

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[0057] log(b) is the non-absorbent wavelength λ NIt can also be calculated from the transmitted light intensity of the light having a wavelength of 100 nm or more, and can be converted from the following formula (XII) to the following formula (XIII), and by substituting this into formula (XI), the above formula (V) can be obtained.

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[0058] [Fourth embodiment] As shown in FIG. 13, a concentration ratio measuring device 10 according to one embodiment of the present disclosure will be described taking as an example an embodiment in which a concentration ratio measuring method is implemented to obtain the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane in a solution S flowing through a flow-through type measurement cell 1a. The concentration ratio measuring device 10 has an absorbance measuring unit 1 that measures the absorbance of the solution S at a specific wavelength, and a concentration ratio calculating unit 2 that calculates the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane in the solution S based on the measured and corrected absorbance and a prerecorded calibration curve. The absorbance measuring unit 1 has a flow-through type measurement cell 1a through which the solution S flows, a light source 1b that irradiates the solution S flowing through the measurement cell 1a with a light beam L1, and an absorbance detector 1c that receives transmitted light L2 that has passed through the solution S. The absorbance measuring unit 1 may further have a memory unit 5 that stores the calibration curve.

[0059] Here, the light ray L1 has a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N Includes. The correction wavelength λ C the product of the molar absorption coefficient of toluene and the molar concentration of toluene at C and the product of the molar absorption coefficient of methylcyclohexane in the above-mentioned solution are approximately equal to each other. The specific wavelength λ S is one or more wavelengths or wavelength ranges in the near infrared wavelength range of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less. The non-absorption wavelength λ N The molar absorption coefficient of toluene at the non-absorption wavelength λ N The molar absorption coefficient of methylcyclohexane in each of these is approximately zero. The absorbance detector 1c receives the transmitted light L2 and calculates a correction wavelength λ based on the optical path length D. C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N The absorbance at is detected and measured.

[0060] The concentration ratio calculation unit 2 and the storage unit 5 may be a single device equipped with an operation unit and a display unit, and may further be equipped with a control unit that controls the operation of the absorbance measurement unit. The concentration ratio calculation unit 2 and the storage unit 5 may be incorporated into a single computer. The absorbance measurement unit 1 may be a single device, and the absorbance measurement unit 1 and the concentration ratio calculation unit 2 may be connected to each other via wire or wirelessly.

[0061] The absorbance may be largely dependent on the temperature of the solution. In addition, when a solution in the reaction process of the synthesis reaction or dehydrogenation reaction of methylcyclohexane flows through the measurement cell 1a, the temperature of the solution in the reaction process may be as high as 80° C. or higher. Therefore, in order to measure the absorbance accurately, the temperature of the solution S flowing through the measurement cell 1a may be converted to a constant temperature by, for example, arranging a heat exchanger upstream of the measurement cell 1a. The constant temperature is not particularly limited and can be appropriately selected depending on the purpose as long as a stable absorbance can be obtained, and may be, for example, about 25°C.

[0062] [Fifth embodiment] The concentration ratio measuring device 10 in the fourth embodiment is an embodiment in which the absorbance of the solution S flowing through the flow-through type measurement cell 1a is continuously measured, but the present invention is not limited to this embodiment. As shown in FIG. 14, the fifth embodiment of the concentration ratio measuring device 20 may be an embodiment that implements a batch-type concentration ratio measuring method in which a light beam L1 is transmitted to a solution S sampled in a fractional measurement cell 1a' and transmitted light L2 that has passed through the solution S is received.

[0063] In addition, the concentration ratio measuring device 20 shown in Figure 14 can appropriately adopt a configuration similar to that of the concentration ratio measuring device 10 shown in Figure 13, except that it has a fractional type measurement cell 1a' instead of the flow-through type measurement cell 1a. Here, the method for sampling the solution S into the preparative measurement cell 1a' is not particularly limited, and may be performed manually or automatically.

[0064] <<Measurement cell>> The measurement cell is not particularly limited and can be appropriately selected depending on the purpose. Examples of the measurement cell include a flow-through type measurement cell and a fractional type measurement cell. The material of the portion of the measuring cell through which light passes can be appropriately selected depending on the specific wavelength, solution composition, etc., and examples thereof include quartz glass.

[0065] <<Light source>> The light source has a correction wavelength λ C , and a specific wavelength λ S and optionally a non-absorbing wavelength λ N As long as it contains the above, there is no particular limitation and it can be appropriately selected depending on the purpose. Examples of the light source include laser light, light emitting diode (LED), and halogen lamp.

[0066] <<Lens>> The lenses can be arranged at various positions on the optical path to converge or collimate light, such as light irradiated from a light source, light irradiated onto a measurement cell, light transmitted through a measurement cell, and light input to an absorbance detector.

[0067] <<Spectrometer>> The spectrometer has a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N As long as the light transmits light, there is no particular limitation and the light source can be appropriately selected depending on the purpose. Examples of the light source include an optical filter, a prism, and a diffraction grating. These may be used alone or in combination of two or more. Examples of the optical filter include a bandpass filter that transmits a specific monochromatic light or a plurality of wavelength ranges, a longpass filter that transmits wavelengths longer than the cut-on wavelength, a shortpass filter that transmits wavelengths shorter than the cut-off wavelength, a cut-off filter that does not transmit a specific monochromatic light or a plurality of wavelength ranges, a colored glass filter, and a dichroic filter. Moreover, as the spectrometer, a combination of a variable optical filter capable of changing the transmission wavelength range and a variable optical attenuator can also be suitably used.

[0068] <<Optical fiber>> In order to efficiently transmit light such as light irradiated from a light source to a measurement cell and transmitted light passing through the measurement cell and input to an absorbance detector, the concentration ratio measuring device may use an optical fiber between the light source and the measurement cell, or between the measurement cell and the absorbance detector.

[0069] <<Absorbance detector>> The absorbance detector has a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N As long as it is possible to detect the above, the detector may be appropriately selected depending on the purpose without any particular limitation. Examples of the detector include optical semiconductors (photocells) and photomultipliers. The absorbance detector converts the transmitted light into an electrical signal to obtain a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N The absorbance of the solution at 25° C. can be measured.

[0070] As a fourth embodiment, a concentration ratio measuring method and a concentration ratio measuring device having a suitable combination of a light source and a spectroscope will be described. The fourth embodiment can be applied to, for example, either the concentration ratio measuring device 10 shown in FIG. 13 or the concentration ratio measuring device 20 shown in FIG.

[0071] [Sixth embodiment] The sixth embodiment is an embodiment of a concentration ratio measuring device that uses a combination of a light source that irradiates monochromatic light of a specific wavelength and a spectrometer such as a bandpass filter that transmits monochromatic light of a specific wavelength, and a concentration ratio measuring method that uses the concentration ratio measuring device. Correction wavelength λ C Monochromatic light of a specific wavelength λ S By switching between these two monochromatic lights, the absorbance at each wavelength can be measured.

[0072] In any of the third to sixth embodiments, the spectroscope may be a pre-spectroscope provided on the optical path between the light source and the measurement cell (see Figures 15 to 16), or a post-spectroscope provided on the optical path between the measurement cell and the absorbance detector (see Figure 17). In the case of the pre-spectroscopic method, the spectrometer may be provided after the light source as shown in FIG. 15, or may be provided before the measurement cell as shown in FIG. In the sixth embodiment, the position at which the spectroscope is provided can be appropriately selected, but it is preferable to provide it behind the light source or before the measurement cell as shown in FIGS.

[0073] According to the sixth embodiment, the correction wavelength λ C , and a specific wavelength λ S By measuring the absorbance based on monochromatic light and calculating the concentration ratio, a monochromatic light absorbance measuring device can be used, and the measurement and calculation can be simplified.

[0074] [Seventh embodiment: Concentration ratio measuring device] The seventh embodiment is a light source that irradiates continuous light and a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N The present invention relates to an embodiment of a concentration ratio measuring device that uses a spectroscope, such as a bandpass filter or cutoff filter, that transmits light, in combination with a concentration ratio measuring device, and a concentration ratio measuring method that uses the concentration ratio measuring device.

[0075] According to the seventh embodiment, the correction wavelength λ C Based on the absorbance of the solution measured at a specific wavelength λ S Since the absorbance of the solution measured in can be corrected, the concentration ratio of the toluene- to methylcyclohexane-containing solution can be measured in real time over a wide concentration range for a long period of time. In addition, the absorbance can be measured based on a specific wavelength in a wide wavelength range or multiple wavelength ranges, and the concentration ratio can be calculated, thereby making it possible to obtain a highly accurate concentration ratio.

[0076] [Eighth embodiment] The eighth embodiment is a concentration ratio measuring device that uses a combination of a light source that irradiates continuous light and a spectrometer that transmits monochromatic light of a specific wavelength using a tunable optical filter that can change the transmission wavelength range, and an embodiment that performs a concentration ratio measuring method using the concentration ratio measuring device. The position where the spectrometer is provided can be appropriately selected, but it is preferable to provide it in front of the absorbance detector as shown in FIG. By switching the tunable optical filter with external control, the correction wavelength λ C , and a specific wavelength λ S can be selected and the absorbance at each wavelength can be measured.

[0077] [Ninth embodiment] The ninth embodiment is a concentration ratio measuring device that uses a light source that irradiates continuous light in combination with a monochromator that extracts monochromatic light of a specific wavelength as a spectroscope, and an embodiment that performs a concentration ratio measuring method using the concentration ratio measuring device. The monochromator is a spectroscope having a mechanism for extracting light of a specific wavelength from an exit slit from light dispersed by a dispersive element such as a prism or a diffraction grating. The position where the spectroscope is provided can be appropriately selected, but it is preferable to provide it behind the light source as shown in FIG. The monochromator corrects the wavelength λ C , and a specific wavelength λ S can be selected and the absorbance at each wavelength can be measured.

[0078] [Tenth embodiment: one specific wavelength λ S Concentration ratio measurement method based on Hereinafter, an embodiment of the concentration ratio measuring method according to the type of specific wavelength to be measured will be described. The concentration ratio measuring method in the tenth embodiment can be suitably carried out by any of the concentration ratio measuring devices 10, 20, 30, 40, and 50 shown in FIGS. 13 to 17, but will be described representatively with reference to FIG. The concentration ratio measuring device 10 calculates the concentration ratio of toluene and methylcyclohexane in the solution S based on the absorbance of transmitted light L2 transmitted through the solution S when a light beam L1 from a light source 1b is irradiated onto the solution S and the optical path length D. The concentration ratio measuring method includes an absorbance measuring step and a concentration ratio calculating step, and may further include a wavelength setting step and a calibration curve creating step, as necessary.

[0079] <Wavelength setting process> The wavelength setting process is a correction wavelength λ C , specific wavelength λ S , and optionally a non-absorbing wavelength λ N This is the process of setting the Specific wavelength λ S When setting, a specific wavelength is set which is one or more wavelengths or wavelength ranges in the seven wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less. The specific wavelength λ S The wavelengths are one or more wavelengths or wavelength ranges among the seven wavelength ranges, and may be one wavelength, two or more wavelengths or wavelength ranges, or two wavelengths, and any embodiment can be suitably applied depending on the purpose.

[0080] There are no particular limitations on the method for setting a specific wavelength, and any known method can be appropriately selected depending on the purpose, and examples thereof include a method for setting a light source capable of irradiating monochromatic light of a specific wavelength in the concentration ratio measuring device of the sixth embodiment; a method for setting a spectrometer such as a bandpass filter or cutoff filter that transmits a specific wavelength in a wide wavelength range or multiple wavelength ranges in the concentration ratio measuring device of the seventh embodiment; a method for setting the transmission wavelength of a variable optical filter to monochromatic light of a specific wavelength in the concentration ratio measuring device of the eighth embodiment; a method for setting the wavelength of a monochromator to monochromatic light of a specific wavelength in the concentration ratio measuring device of the ninth embodiment; and a method for specifying a specific wavelength to be used for calculation in a concentration ratio calculation unit.

[0081] <Calibration curve creation process> In the calibration curve creation process, standard solutions having a graded concentration ratio, in which the concentration ratio t:m of toluene and the concentration m of methylcyclohexane is clear, are prepared in advance, and the desired or set specific wavelength λ S The absorbance at each concentration is measured, and a calibration curve showing linearity between the concentration ratio and the absorbance is prepared.

[0082] The method for creating a calibration curve is not particularly limited and a known method can be appropriately selected depending on the purpose, and for example, a calibration curve can be created by the method described in the Examples below and shown in Figure 1. Furthermore, the created calibration curve can be stored in a memory unit. Examples of the stepwise concentration ratios in the standard solution include the concentration ratios t:m (volume ratio) of the concentration t of toluene to the concentration m of methylcyclohexane, which are 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively.

[0083] <Absorbance measurement process> In the absorbance measurement step, the absorbance at a specific wavelength of the solution to be measured (i.e., the concentration ratio is unknown) is measured. In a seventh embodiment, the specific wavelength is one wavelength. The method for measuring absorbance is not particularly limited and any known method can be appropriately selected depending on the purpose. Specifically, the absorbance can be measured by the following steps A to C. Step A: The amount of transmitted light T0 at a specific wavelength of a blank measurement cell containing no solution is measured. Step B: The amount of light T transmitted through a measuring cell containing the solution at a specific wavelength is measured. Step C: Calculate the absorbance A at a specific wavelength based on the transmittance T / T0 and the following formula (1).

[0084]

number

[0085] <Concentration ratio calculation process> In the concentration ratio calculation step, a concentration ratio t:m between the concentration t of the toluene and the concentration m of the methylcyclohexane is calculated based on the absorbance obtained in the absorbance measurement step and a prerecorded calibration curve. The method for calculating the concentration ratio t:m is not particularly limited and any known method can be appropriately selected depending on the purpose. Specifically, the concentration ratio t:m can be calculated based on the calibration curve and the following formula (2).

[0086]

number

[0087] [Eleventh embodiment: Concentration ratio measurement method based on two or more wavelengths or wavelength ranges] The concentration ratio measurement method of the eleventh embodiment is an embodiment in which the specific wavelength is two or more wavelengths or wavelength ranges. Except for being based on two or more wavelengths or wavelength ranges, the method can be carried out in the same manner as the tenth embodiment. In order to obtain the concentration ratio, the absorbance at any wavelength at a specific wavelength where the linearity between the concentration ratio and the absorbance is excellent may be measured as shown in the tenth embodiment. However, by measuring the absorbance at two or more wavelengths or wavelength ranges and using the average absorbance as shown in the eleventh embodiment, a more stable and accurate measurement can be realized.

[0088] The specific wavelength is two or more wavelengths λ1,...λ n (n is an integer of 2 or more), the resulting absorbances A(λ1), A(λ n ) was measured, and the average absorbance A mean Next, in the seventh embodiment, A(λ1) in formula (2) is replaced with A mean By substituting the above, the concentration ratio can be calculated.

[0089] If the specific wavelength is in the wavelength range from λ1 to λ2, the average digital or analog absorbance A in that wavelength range is mean In the seventh embodiment, A(λ1) in formula (2) is replaced with A mean By substituting the above, the concentration ratio can be calculated. Average absorbance A mean The method for determining the absorbance can be appropriately selected depending on the specifications of the concentration ratio measuring device used, and examples thereof include a digital method in which the average absorbance is determined by integrating and averaging the absorbance for each wavelength measured with a predetermined wavelength resolution for a specific wavelength in a set wavelength range; and a method in which light in a specific wavelength range is irradiated using an optical filter such as a bandpass filter, the transmitted light is collected, and the absorbance in that wavelength range is determined in an analog manner.

[0090] In an eleventh embodiment, the specific wavelengths are two or more wavelengths or wavelength ranges, i.e., two or more wavelengths or wavelength ranges in the seven wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less. The wavelength range is not particularly limited as long as it is within the range of any of the seven wavelength ranges (i.e., wavelength ranges with a coefficient of determination close to 1 shown in Table 2 below) and can be appropriately selected depending on the purpose. The wavelength width Δλ of the wavelength range is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include 5 [nm], 10 [nm], and 20 [nm]. Many commercially available optical filters have a half-width of 10 nm or 20 nm, and these filters can be used suitably. Alternatively, the average absorbance may be calculated in an analog manner using an optical filter having an arbitrary half-width or a variable optical filter capable of changing the transmission wavelength range, or the digital method described above may be used.

[0091] Compared to the absorbance measured at one wavelength, the average absorbance improves the coefficient of determination, and therefore allows for more linear measurements. In addition, the total amount of transmitted light increases, reducing the effects of measurement errors of wavelength and transmitted light, and improving the S / N ratio. Therefore, according to the concentration ratio measuring method of the eighth embodiment, it is possible to measure the concentration ratio more stably and with higher accuracy.

[0092] [Twelfth embodiment: Concentration ratio measurement method based on wavelength range with small wavelength dependency] The concentration ratio measurement method of the twelfth embodiment is an embodiment based on a wavelength range with small wavelength dependency, and can be carried out in the same manner as the tenth and eleventh embodiments, except that it is based on a wavelength range with small wavelength dependency. The specific wavelengths in the twelfth embodiment are one or more wavelengths or wavelength ranges in a wavelength range with small wavelength dependency, that is, one or more wavelengths or wavelength ranges in the wavelength ranges of 1730 nm to 1850 nm and 1800 nm to 2050 nm.

[0093] Absorbance has wavelength dependency. The smaller this wavelength dependency, the more stable the measurement. If the wavelength dependency is large, the change in absorbance will be large for a small change in the measurement wavelength, and if there is any fluctuation in the measurement wavelength, the reproducibility will deteriorate. This means that the error sensitivity is high, which is one of the factors that cause unstable measurements. Therefore, from the viewpoint of reducing errors resulting from fluctuations in the measured wavelength and performing accurate measurements, it is advisable to select a wavelength range with small wavelength dependency (good flatness). As is clear from Table 4 in the Examples described below, it is preferable to select a wavelength range of 1730 nm or more and 1850 nm or less, and a wavelength range of 1800 nm or more and 2050 nm or less. According to the concentration ratio measuring method of the twelfth embodiment, errors resulting from fluctuations in the measurement wavelength can be reduced, and highly accurate measurements can be performed.

[0094] [Thirteenth embodiment: Concentration ratio measurement method based on wavelength range with high absorbance sensitivity] The concentration ratio measurement method of the thirteenth embodiment is an embodiment based on a wavelength range with high absorbance sensitivity, and can be carried out in the same manner as the seventh to ninth embodiments, except that it is based on a wavelength range with high absorbance sensitivity. The specific wavelengths in the thirteenth embodiment are one or more wavelengths or wavelength ranges in the wavelength range with high absorbance sensitivity, i.e., one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

[0095] While the smaller the wavelength dependency, the more stable the measurement, the concentration ratio of toluene and methylcyclohexane changes depending on the progress of the hydrogenation / dehydrogenation reaction of toluene and methylcyclohexane. Therefore, in order to know the direction of the change (hydrogenation or dehydrogenation) and the dynamics of the change, it is best to measure the absorbance in the wavelength range with the greatest sensitivity. Specifically, it is preferable to select a wavelength range from 1120 nm to 1140 nm, from 1190 nm to 1230 nm, from 1620 nm to 1680 nm, from 2150 nm to 2180 nm, or from 2360 nm to 2420 nm. According to the concentration ratio measuring method of the thirteenth embodiment, it is possible to perform measurements with high sensitivity to changes in concentration ratio.

[0096] As in the twelfth and thirteenth embodiments, the measurement wavelength can be changed depending on the purpose. In other words, when monitoring concentration ratios, measurements are made in a wavelength range where the coefficient of determination is close to 1 and where the wavelength dependency of absorbance is small (good flatness). On the other hand, when checking the direction or dynamics of a reaction, or checking minute changes in the conversion rate in the final stage of a reaction, measurements are made in a wavelength range where the sensitivity of absorbance to the concentration ratio is high (the absolute value of the slope a, |a|, is large). EXAMPLES

[0097] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0098] 1 is a graph showing the relationship between the concentration ratio of toluene and methylcyclohexane and absorbance. Specifically, it shows the absorbance of a solution in which toluene and methylcyclohexane are mixed at a predetermined concentration ratio at wavelengths of 1000 [nm] to 2500 [nm]. In Fig. 1, the vertical axis indicates absorbance, and the horizontal axis indicates wavelength. Solutions (represented as T00M100, T10M90, T30M70, T50M50, T70M30, and T100M00 in Fig. 8) were prepared so that the concentration ratio t:m of the concentration t of toluene to the concentration m of methylcyclohexane was 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively, in terms of volume [L], and the absorbance of each solution was measured at wavelengths of 1000 [nm] to 2500 [nm].

[0099] It can be seen from FIG. 1 that the absorbance exhibits a specific value for each wavelength depending on a given concentration ratio (volume %) of toluene and methylcyclohexane.

[0100] Next, in order to evaluate the correlation between the absorbance and the concentration ratio t:m shown in FIG. 1, the coefficient of determination between the absorbance and the concentration ratio t:m was calculated and shown in FIG. 2, which is superimposed on the graph of FIG. FIG. 2 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination. In Figure 2, the bold line indicates the coefficient of determination R 2 (Correlation coefficient R squared: R 2 ) and the right vertical axis indicates the coefficient of determination. Other legends are the same as in Figure 1.

[0101] In FIG. 2, the coefficient of determination indicates the linearity between absorbance and the concentration ratio t:m. 2 , 0≦R 2 The value is ≦1, and the closer it is to 1, the more linear the relationship is.

[0102] Toluene concentration c T The relationship between and absorbance is expressed by the following equation (2).

[0103]

number

[0104] A(λ1): absorbance at specific wavelength λ1 [AU] αT (λ1): Molar absorption coefficient of toluene at λ1 [L mol -1 ·cm -1 ] α M (λ1): Molar absorption coefficient of methylcyclohexane at λ1 [L mol -1 ·cm -1 ] D: Optical path length [cm] c T : Molar concentration of toluene [mol L -1 ] c M : Molar concentration of methylcyclohexane [mol L -1 ] t: Concentration ratio of toluene in the solution (volume ratio) m: Concentration ratio (volume ratio) of methylcyclohexane in the solution where t+m=1

[0105] Here, according to the reaction formulas (1) and (2) above, the hydrogenation / dehydrogenation reaction of toluene and methylcyclohexane is an equimolar reaction, and therefore the concentration ratio can be expressed as t:m=t:1-t. By substituting into equation (2), the absorbance A(λ) of the solution can be expressed as a linear equation in terms of the toluene concentration t. FIG. 2 shows a graph showing the strength of the relationship between toluene concentration t and absorbance A(λ) as a coefficient of determination. As can be seen from Figure 2, in the wavelength range of 1100[nm] to 2500[nm], the absorbance value varies between 0[AU] and 2.6[AU]. Referring to the correspondence between absorbance and transmittance shown in Table 1, when the absorbance of 0[AU] to 2.6[AU] is expressed as transmittance T / T0, it is equivalent to a change of 100[%] to 0.25[%].

[0106] [Table 1]

[0107] The relationship between absorbance and transmittance is given by the following formula (1).

number

[0108] From Figure 2 and Table 1, due to the dynamic characteristics of the sensor and filter, the linearity characteristics decrease when the absorbance A is 0.05 [AU] or less, or when the wavelength is 1.3 [AU] or more. This is equivalent to a transmittance T / T0 of 89.1% or more and 5.0% or less.

[0109] From these results, it was found that there is an optimal wavelength range for determining the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane, as shown in Table 2, and that the concentration ratio can be accurately determined by measuring the absorbance of a solution using a specific wavelength that is one or more wavelengths or a wavelength range in the wavelength range shown in Table 2. It was confirmed that it is not necessary to measure absorbance in all wavelength ranges, but rather that it is possible to measure absorbance at one of the most suitable wavelength ranges shown in Table 2 and calculate the concentration ratio.

[0110] [Table 2]

[0111] The present invention is not limited to the configurations shown in the above embodiments, combinations with other elements, etc. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of symbols]

[0112] 10, 20: Concentration ratio measuring device 1: Absorbance measurement section 1a, 1a': Measuring cell 1b:Light source 1c: Absorbance detector 2: Concentration ratio calculation section 3: Spectrometer 5: Memory unit L1: Light ray L2: Transmitted light S: Solution D: Optical path length

Claims

1. A method for measuring a concentration ratio of a solution containing toluene to methylcyclohexane, comprising the steps of: Correction wavelength λ at the start of measurement T0 Ｃ The absorbance A (λ Ｃ ) Ｔ０ and, After a predetermined time has elapsed, the correction wavelength λ Ｃ The absorbance A (λ Ｃ ) Ｔ１ and, After a predetermined time has elapsed, the specific wavelength λ of T1 Ｓ The absorbance A (λ Ｓ ) Ｔ１ and measuring The absorbance A (λ Ｓ ) Ｔ１ is corrected to obtain the correction value A'(λ Ｓ ) Ｔ１ Calculate [0010] The correction value A′(λ Ｓ ) Ｔ１ and calculating a concentration ratio t:m of the concentration t of the toluene and the concentration m of the methylcyclohexane based on a previously recorded calibration curve based on the above formula (1), The correction wavelength λ Ｃ the product of the molar absorption coefficient of toluene and the molar concentration of toluene at Ｃ and the product of the molar absorption coefficient of methylcyclohexane and the molar concentration of methylcyclohexane in the The specific wavelength λ Ｓ is one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

2. The correction wavelength λ Ｃ The concentration ratio measuring method according to claim 1, wherein the wavelength is one or more of 1160 nm to 1166 nm, 1694 nm to 1707 nm, 2086 nm to 2090 nm, and 2274 nm to 2284 nm.

3. The absorbance A(λ Ｃ ) Ｔ１ The absorbance A (λ Ｃ ) Ｔ０ The ratio A (λ Ｃ ) Ｔ０ / A(λ Ｃ ) Ｔ１ The concentration ratio measuring method according to claim 1 or 2, further comprising a step of determining whether a predetermined band value is satisfied, continuing the measurement if the predetermined band value is satisfied, and terminating the measurement if the predetermined band value is not satisfied.

4. After a predetermined time has elapsed, the non-absorption wavelength λ of T1 Ｎ The absorbance A (λ Ｎ ) Ｔ１ and measuring The absorbance A(λ Ｎ ) Ｔ１ and determining whether the measured value satisfies a predetermined band value, continuing the measurement if the measured value satisfies the predetermined band value, and terminating the measurement if the measured value does not satisfy the predetermined band value. The non-absorption wavelength λ Ｎ The molar absorption coefficient of toluene at the non-absorption wavelength λ Ｎ 3. The method for measuring a concentration ratio according to claim 1, wherein the molar absorption coefficient of methylcyclohexane in

5. The non-absorption wavelength λ Ｎ The concentration ratio measuring method according to claim 4, wherein the wavelength is one or more of 1000 nm or more and 1100 nm or less, 1300 nm or more and 1340 nm or less, and 1540 nm or more and 1600 nm or less.

6. Non-absorption wavelength λ at the start of measurement T0 Ｎ The transmitted light intensity I (λ Ｎ ) Ｔ０ and the non-absorption wavelength λ after a predetermined time T1 has elapsed. Ｎ The transmitted light intensity I (λ Ｎ ) Ｔ１ and measuring Based on the following formula (V), a specific wavelength λ of T1 after a predetermined time has elapsed Ｓ The absorbance A (λ Ｓ ) Ｔ１ is corrected to obtain the correction value A″(λ Ｓ ) Ｔ１ The method for measuring a concentration ratio according to claim 1 or 2, further comprising the step of: [0025]

7. A concentration ratio measuring device for measuring the concentration ratio of a solution containing toluene to methylcyclohexane, Correction wavelength λ Ｃ , and a specific wavelength λ Ｓ an absorbance measuring unit that measures the absorbance of the solution in Correction wavelength λ at the start of measurement T0 Ｃ The absorbance A (λ Ｃ ) Ｔ０ , the correction wavelength λ of T1 after a predetermined time has elapsed Ｃ The absorbance A (λ Ｃ ) Ｔ１ and a specific wavelength λ of T1 after a predetermined time has elapsed based on the following formula (I): Ｓ The absorbance A (λ Ｓ ) Ｔ１ is corrected to obtain the correction value A'(λ Ｓ ) Ｔ１ Calculate [0030] The correction value A′(λ Ｓ ) Ｔ１ a concentration ratio calculation unit that calculates a concentration ratio t:m of the concentration t of the toluene and the concentration m of the methylcyclohexane based on a previously recorded calibration curve based on the above-mentioned. having The correction wavelength λ Ｃ the product of the molar absorption coefficient of toluene and the molar concentration of toluene at Ｃ and the product of the molar absorption coefficient of methylcyclohexane and the molar concentration of methylcyclohexane in the The specific wavelength λ Ｓ is one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

8. The correction wavelength λ Ｃ 8. The concentration ratio measuring device according to claim 7, wherein the wavelength is one or more of 1160 nm to 1166 nm, 1694 nm to 1707 nm, 2086 nm to 2090 nm, and 2274 nm to 2284 nm.

9. The absorbance A(λ Ｃ ) Ｔ１ The absorbance A (λ Ｃ ) Ｔ０ The ratio A (λ Ｃ ) Ｔ０ / A(λ Ｃ ) Ｔ１ The concentration ratio measurement device according to claim 7 or 8, further comprising a first discrimination unit that determines whether a predetermined band value is satisfied, continues the measurement if the predetermined band value is satisfied, and terminates the measurement if the predetermined band value is not satisfied.

10. The absorbance measurement unit detects a non-absorption wavelength λ of T1 after a predetermined time has elapsed. Ｎ The absorbance A (λ Ｎ ) Ｔ１ Further measuring The concentration ratio measuring device detects the non-absorption wavelength λ of T1 after a predetermined time has elapsed. Ｎ The absorbance A (λ Ｎ ) Ｔ１ a second determination unit that determines whether or not the predetermined band value is satisfied, continues the measurement if the predetermined band value is satisfied, and ends the measurement if the predetermined band value is not satisfied, The non-absorption wavelength λ Ｎ The molar absorption coefficient of toluene at the non-absorption wavelength λ Ｎ 9. The concentration ratio measuring device according to claim 7, wherein the molar absorption coefficient of methylcyclohexane in

11. The non-absorption wavelength λ Ｎ The concentration ratio measuring device according to claim 10 , wherein the wavelength is one or more of 1000 nm to 1100 nm, 1300 nm to 1340 nm, and 1540 nm to 1600 nm.

12. The absorbance measurement unit detects a non-absorption wavelength λ at the start of measurement T0. Ｎ The transmitted light intensity I (λ Ｎ ) Ｔ０ and the non-absorption wavelength λ after a predetermined time T1 has elapsed. Ｎ The transmitted light intensity I (λ Ｎ ) Ｔ１ Further measuring The concentration ratio calculation unit calculates a specific wavelength λ after a predetermined time T1 based on the following formula (V): Ｓ The absorbance A (λ Ｓ ) Ｔ１ is corrected to obtain the correction value A″(λ Ｓ ) Ｔ１ The concentration ratio measuring device according to claim 7 or 8, wherein the concentration ratio measuring device calculates: [0045]

13. 9. The concentration ratio measurement device according to claim 7, wherein the absorbance measurement unit comprises a measurement cell, a light source that irradiates the solution contained in the measurement cell with light of the specific wavelength, and an absorbance detector that measures the absorbance of the transmitted light that has passed through the solution.

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